Notes on CBC Parameters and Indices

CBC parameters are discussed with reference to Rodak’s Hematology Clinical Principles and Application, 6th Ed., Chapter 13 (pp. 211-212) and related sources.
Key emphasis: WBC count, WBC differential (relative counts in %), and absolute WBC counts; morphology and interpretation of immature cells; left shift; and how these relate to disease processes.

WBC count (x 10^9/L) reports total leukocytes measured by the analyzer.
WBC differential (5 types) provides relative counts in % for the five leukocyte types, generated by automated analyzers or manual review.
Absolute WBC counts equal the actual number of each cell type (e.g., Absolute Neutrophil Count, ANC).
Relative counts (percent) versus absolute counts (numbers) are both essential for diagnosis.
WBC morphology includes size, interior structure (N:C ratio, nucleus density, granularity) and can be plotted on scatterplots to differentiate cell populations;
Immature cells detected by morphology may indicate leukemias or infections.
Left shift refers to an increase in neutrophils with bands and sometimes metamyelocytes, commonly due to infection.
WBC parameters are summarized as:
- Relative count: differential count values expressed as percentages (%).
- Absolute count: differential count values expressed as actual numbers of each cell type (e.g., ANC).
Reference: Rodak’s Hematology Clinical Principles and Application, 6th Ed., Chapter 13, pp 211-212.

Formula:
ext{Absolute count} = rac{ ext{Relative %}}{100} imes ext{Total WBC count}
where Total WBC count is given in x 10^9/L.
Example 1:
- Total WBC =
  $8.5 imes 10^{9}/L$ , Relative neutrophils = 53%
- ANC =
  $$0.53 imes 8.5 imes 10^{9}/L = 4.505 imes 10^{9}/L \